Fix erroneous protected-broadcast check

This happens because isPermittedShellBroadcast() is called twice,
one for runtime receivers and the other manifest receivers, and
when SysUI sends a broadcast to its own runtime receiver, another
check also happens for manifest receivers but there's no receivers.

Fixes: 77154348
Test: Manual test with the following steps:
- adb shell dumpsys battery unplug
- adb shell settings delete secure low_power_manual_activation_count
- adb shell settings delete secure low_power_warning_acknowledged
- adb shell settings delete secure suppress_auto_battery_saver
- Then enable battery saver
- Make sure there's no error on logcat.

Change-Id: I9e4305016e10059bd067f06d05433102864b2036